Daniel is 16 years older than Ishaan. Eighteen years ago, Daniel was 3 times as old as Ishaan. How old is Ishaan now?
Solution: We can use the given information to write down two equations that describe the ages of Daniel and Ishaan. Let Daniel's current age be $d$ and Ishaan's current age be $i$ The information in the first sentence can be expressed in the following equation: $d = i + 16$ Eighteen years ago, Daniel was $d - 18$ years old, and Ishaan was $i - 18$ years old. The information in the second sentence can be expressed in the following equation: $d - 18 = 3(i - 18)$ Now we have two independent equations, and we can solve for our two unknowns. Because we are looking for $i$ , it might be easiest to use our first equation for $d$ and substitute it into our second equation. Our first equation is: $d = i + 16$ . Substituting this into our second equation, we get the equation: $(i + 16)$ $-$ $18 = 3(i - 18)$ which combines the information about $i$ from both of our original equations. Simplifying both sides of this equation, we get: $i - 2 = 3 i - 54$ Solving for $i$ , we get: $2 i = 52$ $i = 26$.